Lei Xie, Qian Du, Guang Liu, Zengyan Lian, Yaguang Xie, Yifu Luo
Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines. They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the effect of the nozzle guide vanes. To avoid hot mainstream gas ingress, the cavity is usually purged by a stream of sealing flow. The interactions between the external crossflow, cavity flow, and sealing flow are complicated and involve all scales of turbulent unsteadiness and flow instability which are beyond the resolution of the Reynolds-average approach. To cope with such a complex issue, a wall-modeled large-eddy simulation (WMLES) approach is adopted in this study. In the simulation, a 20° sector model is used and subjected to a uniform pre-swirled external crossflow and a stream of radial sealing flow. It is triggered by a convergent Reynolds-averaged Navier-Stokes (RANS) result in which the shear stress transport (SST) turbulent model is used. In the WMLES simulation, the Smagoringsky sub-grid scale (SGS) model is applied. A scalar transportation equation is solved to simulate the blending and transportation process in the cavity. The overall flow field characteristics and deviation between RANS and WMLES results are discussed first. Both RANS and WMLES results show a Batchelor flow mode, while distinct deviation is also observed. Deviations in the small-radius region are caused by the insufficiency of the RANS approach in capturing the small-scale vortex structures in the boundary layer while deviations in the large-radius region are caused by the insufficiency of the RANS approach in predicting the external crossflow ingestion. The boundary layer vortex and external ingestion are then discussed in detail, highlighting the related flow instabilities. Finally, the large-flow structures induced by external flow ingress are analyzed using unsteady pressure oscillation signals.
{"title":"Investigation of flow characteristics in a rotor-stator cavity under crossflow using wall-modelled large-eddy simulation","authors":"Lei Xie, Qian Du, Guang Liu, Zengyan Lian, Yaguang Xie, Yifu Luo","doi":"10.1631/jzus.A2200565","DOIUrl":"https://doi.org/10.1631/jzus.A2200565","url":null,"abstract":"Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines. They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the effect of the nozzle guide vanes. To avoid hot mainstream gas ingress, the cavity is usually purged by a stream of sealing flow. The interactions between the external crossflow, cavity flow, and sealing flow are complicated and involve all scales of turbulent unsteadiness and flow instability which are beyond the resolution of the Reynolds-average approach. To cope with such a complex issue, a wall-modeled large-eddy simulation (WMLES) approach is adopted in this study. In the simulation, a 20° sector model is used and subjected to a uniform pre-swirled external crossflow and a stream of radial sealing flow. It is triggered by a convergent Reynolds-averaged Navier-Stokes (RANS) result in which the shear stress transport (SST) turbulent model is used. In the WMLES simulation, the Smagoringsky sub-grid scale (SGS) model is applied. A scalar transportation equation is solved to simulate the blending and transportation process in the cavity. The overall flow field characteristics and deviation between RANS and WMLES results are discussed first. Both RANS and WMLES results show a Batchelor flow mode, while distinct deviation is also observed. Deviations in the small-radius region are caused by the insufficiency of the RANS approach in capturing the small-scale vortex structures in the boundary layer while deviations in the large-radius region are caused by the insufficiency of the RANS approach in predicting the external crossflow ingestion. The boundary layer vortex and external ingestion are then discussed in detail, highlighting the related flow instabilities. Finally, the large-flow structures induced by external flow ingress are analyzed using unsteady pressure oscillation signals.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82556327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hedong Li, Yabiao Li, Yunfeng Pan, NG P.L., C. Leung, Xin Zhao
Slurry-infiltrated fiber concrete (SIFCON) is a sort of strain hardening cement-based composite material, typically made with 5%–20% steel fibers. This study focused on a novel type of SIFCON in which hooked-end steel fibers were replaced by arc-shaped steel fibers. The quasi-static compressive properties of the SIFCON were first measured. Test results suggested that using arc-shaped steel fibers in lieu of hooked-end steel fibers increased the quasi-static compressive strength by 47.1% and the strain at peak stress by 56.3%. We attribute these improvements to new crack-resisting mechanisms, namely “fiber cross-lock”, “dual bridging”, and “confinement loops”, when the arc-shaped steel fibers are introduced into SIFCON. As high impact resistance is a special property of SIFCON that is of practical significance, the dynamic compressive properties of arc-shaped steel fiber SIFCON were studied by using an 80-mm-diameter split Hopkinson pressure bar (SHPB). The results showed that the dynamic compressive strength, dynamic increase factor (DIF), and dynamic toughness of SIFCON all increased with the strain rate. The SIFCON incorporating arc-shaped steel fibers proved to have significant advantages in structural applications requiring high impact resistance.
{"title":"Compressive properties of a novel slurry-infiltrated fiber concrete reinforced with arc-shaped steel fibers","authors":"Hedong Li, Yabiao Li, Yunfeng Pan, NG P.L., C. Leung, Xin Zhao","doi":"10.1631/jzus.A2200405","DOIUrl":"https://doi.org/10.1631/jzus.A2200405","url":null,"abstract":"Slurry-infiltrated fiber concrete (SIFCON) is a sort of strain hardening cement-based composite material, typically made with 5%–20% steel fibers. This study focused on a novel type of SIFCON in which hooked-end steel fibers were replaced by arc-shaped steel fibers. The quasi-static compressive properties of the SIFCON were first measured. Test results suggested that using arc-shaped steel fibers in lieu of hooked-end steel fibers increased the quasi-static compressive strength by 47.1% and the strain at peak stress by 56.3%. We attribute these improvements to new crack-resisting mechanisms, namely “fiber cross-lock”, “dual bridging”, and “confinement loops”, when the arc-shaped steel fibers are introduced into SIFCON. As high impact resistance is a special property of SIFCON that is of practical significance, the dynamic compressive properties of arc-shaped steel fiber SIFCON were studied by using an 80-mm-diameter split Hopkinson pressure bar (SHPB). The results showed that the dynamic compressive strength, dynamic increase factor (DIF), and dynamic toughness of SIFCON all increased with the strain rate. The SIFCON incorporating arc-shaped steel fibers proved to have significant advantages in structural applications requiring high impact resistance.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89473114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High-speed locomotives are prone to carbody or bogie hunting when the wheel-rail contact conicity is excessively low or high. This can cause negative impacts on vehicle dynamics performance. This study presents four types of typical yaw damper layouts for a high-speed locomotive (Bo-Bo) and compares, by using the multi-objective optimization method, the influences of those layouts on the lateral dynamics performance of the locomotive; the linear stability indexes under low-conicity and high-conicity conditions are selected as optimization objectives. Furthermore, the radial basis function-based high-dimensional model representation (RBF-HDMR) method is used to conduct a global sensitivity analysis (GSA) between key suspension parameters and the lateral dynamics performance of the locomotive, including the lateral ride comfort on straight tracks under the low-conicity condition, and also the operational safety on curved tracks. It is concluded that the layout of yaw dampers has a considerable impact on low-conicity stability and lateral ride comfort but has little influence on curving performance. There is also an important finding that only when the locomotive adopts the layout with opening outward, the difference in lateral ride comfort between the front and rear ends of the carbody can be eliminated by adjusting the lateral installation angle of the yaw dampers. Finally, force analysis and modal analysis methods are adopted to explain the influence mechanism of yaw damper layouts on the lateral stability and differences in lateral ride comfort between the front and rear ends of the carbody. 目 的 以中国某型 Bo-Bo 高速机车为研究对象, 分析四种典型的抗蛇行减振器布置方式及横向安装角对机车横向动力学性能和参数匹配关系的影响, 并解释其作用机理. 创新点 1. 通过多目标优化方法来同时优化机车低锥度和高锥度横向稳定性, 获得四种抗蛇行减振器布置方式下机车最优横向动力学性能及横向安装角的不同选取原则; 2. 当抗蛇行减振器横向安装角存在时, 引入抗蛇行减振器附加作用力和作用力矩, 结合车体横向和摇头模态相位差来解释抗蛇行减振器布置方式对机车蛇行稳定性和车体前后横向平稳性差异的影响机理. 方 法 1. 基于搭建的 MATLAB/SIMPACK 联合仿真平台, 采用多目标优化方法得到机车最优横向动力学性能及对应悬挂参数分布结果 (图 4 和 5); 2. 通过拉丁超立方采样对机车直线运行性能和曲线通过性能评价指标进行蒙特卡洛仿真, 并采用基于径向基函数的高维模型表示的敏感性分析方法对关键悬挂参数进行全局敏感性分析 (图 6); 3. 采用根轨迹法分析不同抗蛇行减振器布置方式下横向安装角对机车蛇行稳定性影响规律, 并提取蛇行模态中对应的车体横移和摇头模态相位差 (图 8 和 9). 结 论 1. 抗蛇行减振器的布置方式对机车横向稳定性和平稳性具有显著影响, 且不同布置方式下横向安装角的选取原则存在差异. 2. 全局敏感性分析结果显示: 机车曲线通过性能对抗蛇行减振器阻尼和一系横向刚度的敏感性较强, 但对抗蛇行减振器横向安装角的敏感性较弱. 3. 机车采用抗蛇行减振器开口向外布置时, 优化横向安装角可以减小车体前后端横向平稳性差异, 而机车采用其他三种抗蛇行减振器布置方式时没有这个特点.
{"title":"抗蛇行减振器布置方式对机车横向动力学性能影响: Pareto优化和参数分析","authors":"Guang Li, Yuan Yao, Longjiang Shen, Xiaoxing Deng, Wensheng Zhong","doi":"10.1631/jzus.a2200374","DOIUrl":"https://doi.org/10.1631/jzus.a2200374","url":null,"abstract":"High-speed locomotives are prone to carbody or bogie hunting when the wheel-rail contact conicity is excessively low or high. This can cause negative impacts on vehicle dynamics performance. This study presents four types of typical yaw damper layouts for a high-speed locomotive (Bo-Bo) and compares, by using the multi-objective optimization method, the influences of those layouts on the lateral dynamics performance of the locomotive; the linear stability indexes under low-conicity and high-conicity conditions are selected as optimization objectives. Furthermore, the radial basis function-based high-dimensional model representation (RBF-HDMR) method is used to conduct a global sensitivity analysis (GSA) between key suspension parameters and the lateral dynamics performance of the locomotive, including the lateral ride comfort on straight tracks under the low-conicity condition, and also the operational safety on curved tracks. It is concluded that the layout of yaw dampers has a considerable impact on low-conicity stability and lateral ride comfort but has little influence on curving performance. There is also an important finding that only when the locomotive adopts the layout with opening outward, the difference in lateral ride comfort between the front and rear ends of the carbody can be eliminated by adjusting the lateral installation angle of the yaw dampers. Finally, force analysis and modal analysis methods are adopted to explain the influence mechanism of yaw damper layouts on the lateral stability and differences in lateral ride comfort between the front and rear ends of the carbody. 目 的 以中国某型 Bo-Bo 高速机车为研究对象, 分析四种典型的抗蛇行减振器布置方式及横向安装角对机车横向动力学性能和参数匹配关系的影响, 并解释其作用机理. 创新点 1. 通过多目标优化方法来同时优化机车低锥度和高锥度横向稳定性, 获得四种抗蛇行减振器布置方式下机车最优横向动力学性能及横向安装角的不同选取原则; 2. 当抗蛇行减振器横向安装角存在时, 引入抗蛇行减振器附加作用力和作用力矩, 结合车体横向和摇头模态相位差来解释抗蛇行减振器布置方式对机车蛇行稳定性和车体前后横向平稳性差异的影响机理. 方 法 1. 基于搭建的 MATLAB/SIMPACK 联合仿真平台, 采用多目标优化方法得到机车最优横向动力学性能及对应悬挂参数分布结果 (图 4 和 5); 2. 通过拉丁超立方采样对机车直线运行性能和曲线通过性能评价指标进行蒙特卡洛仿真, 并采用基于径向基函数的高维模型表示的敏感性分析方法对关键悬挂参数进行全局敏感性分析 (图 6); 3. 采用根轨迹法分析不同抗蛇行减振器布置方式下横向安装角对机车蛇行稳定性影响规律, 并提取蛇行模态中对应的车体横移和摇头模态相位差 (图 8 和 9). 结 论 1. 抗蛇行减振器的布置方式对机车横向稳定性和平稳性具有显著影响, 且不同布置方式下横向安装角的选取原则存在差异. 2. 全局敏感性分析结果显示: 机车曲线通过性能对抗蛇行减振器阻尼和一系横向刚度的敏感性较强, 但对抗蛇行减振器横向安装角的敏感性较弱. 3. 机车采用抗蛇行减振器开口向外布置时, 优化横向安装角可以减小车体前后端横向平稳性差异, 而机车采用其他三种抗蛇行减振器布置方式时没有这个特点.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78589521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wen Wang, Yanfeng Zheng, Jingzhe Tang, Chao Yang, Yao-zhi Luo
目的 结构的三维弹塑性接触问题通常包含强非线性, 且计算比较耗时。为解决这类问题, 本文提出基于图形处理器加速的有限质点法。 创新点 1. 发展基于有限质点法的六面体缩减积分单元; 2. 提出结构的三维并行接触算法。 方法 1. 发展基于有限质点法的六面体缩减积分单元, 并采用沙漏控制技术, 用于模拟结构的弹塑性行为; 2. 提出结构的三维并行接触算法, 将包含接触面的三维空间分解为立方体单元格, 仅在相邻单元格之间进行接触搜索, 并使用链式数据结构存储接触质点; 3. 通过基于图形处理器的并行计算技术对算法进行加速。 结论 1. 本文方法与有限元软件Abaqus/Explicit相比, 在总计算时间和接触计算时间上分别提升效率约80倍和340倍; 2. 本文方法的有效性和计算效率都得到了验证。 A graphics processing unit (GPU)-accelerated vector-form particle-element method, i.e., the finite particle method (FPM), is proposed for 3D elastoplastic contact of structures involving strong nonlinearities and computationally expensive contact calculations. A hexahedral FPM element with reduced integration and anti-hourglass is developed to model structural elastoplastic behaviors. The 3D space containing contact surfaces is decomposed into cubic cells and the contact search is performed between adjacent cells to improve search efficiency. A connected list data structure is used for storing contact particles to facilitate the parallel contact search procedure. The contact constraints are enforced by explicitly applying normal and tangential contact forces to the contact particles. The proposed method is fully accelerated by GPU-based parallel computing. After verification, the performance of the proposed method is compared with the serial finite element code Abaqus/Explicit by testing two large-scale contact examples. The maximum speedup of the proposed method over Abaqus/Explicit is approximately 80 for the overall computation and 340 for contact calculations. Therefore, the proposed method is shown to be effective and efficient.
目的 结构的三维弹塑性接触问题通常包含强非线性, 且计算比较耗时。为解决这类问题, 本文提出基于图形处理器加速的有限质点法。 创新点 1. 发展基于有限质点法的六面体缩减积分单元; 2. 提出结构的三维并行接触算法。 方法 1. 发展基于有限质点法的六面体缩减积分单元, 并采用沙漏控制技术, 用于模拟结构的弹塑性行为; 2. 提出结构的三维并行接触算法, 将包含接触面的三维空间分解为立方体单元格, 仅在相邻单元格之间进行接触搜索, 并使用链式数据结构存储接触质点; 3. 通过基于图形处理器的并行计算技术对算法进行加速。 结论 1. 本文方法与有限元软件Abaqus/Explicit相比, 在总计算时间和接触计算时间上分别提升效率约80倍和340倍; 2. 本文方法的有效性和计算效率都得到了验证。 A graphics processing unit (GPU)-accelerated vector-form particle-element method, i.e., the finite particle method (FPM), is proposed for 3D elastoplastic contact of structures involving strong nonlinearities and computationally expensive contact calculations. A hexahedral FPM element with reduced integration and anti-hourglass is developed to model structural elastoplastic behaviors. The 3D space containing contact surfaces is decomposed into cubic cells and the contact search is performed between adjacent cells to improve search efficiency. A connected list data structure is used for storing contact particles to facilitate the parallel contact search procedure. The contact constraints are enforced by explicitly applying normal and tangential contact forces to the contact particles. The proposed method is fully accelerated by GPU-based parallel computing. After verification, the performance of the proposed method is compared with the serial finite element code Abaqus/Explicit by testing two large-scale contact examples. The maximum speedup of the proposed method over Abaqus/Explicit is approximately 80 for the overall computation and 340 for contact calculations. Therefore, the proposed method is shown to be effective and efficient.
{"title":"GPU-accelerated vector-form particle-element method for 3D elastoplastic contact of structures","authors":"Wen Wang, Yanfeng Zheng, Jingzhe Tang, Chao Yang, Yao-zhi Luo","doi":"10.1631/jzus.a2200311","DOIUrl":"https://doi.org/10.1631/jzus.a2200311","url":null,"abstract":"目的 结构的三维弹塑性接触问题通常包含强非线性, 且计算比较耗时。为解决这类问题, 本文提出基于图形处理器加速的有限质点法。 创新点 1. 发展基于有限质点法的六面体缩减积分单元; 2. 提出结构的三维并行接触算法。 方法 1. 发展基于有限质点法的六面体缩减积分单元, 并采用沙漏控制技术, 用于模拟结构的弹塑性行为; 2. 提出结构的三维并行接触算法, 将包含接触面的三维空间分解为立方体单元格, 仅在相邻单元格之间进行接触搜索, 并使用链式数据结构存储接触质点; 3. 通过基于图形处理器的并行计算技术对算法进行加速。 结论 1. 本文方法与有限元软件Abaqus/Explicit相比, 在总计算时间和接触计算时间上分别提升效率约80倍和340倍; 2. 本文方法的有效性和计算效率都得到了验证。 A graphics processing unit (GPU)-accelerated vector-form particle-element method, i.e., the finite particle method (FPM), is proposed for 3D elastoplastic contact of structures involving strong nonlinearities and computationally expensive contact calculations. A hexahedral FPM element with reduced integration and anti-hourglass is developed to model structural elastoplastic behaviors. The 3D space containing contact surfaces is decomposed into cubic cells and the contact search is performed between adjacent cells to improve search efficiency. A connected list data structure is used for storing contact particles to facilitate the parallel contact search procedure. The contact constraints are enforced by explicitly applying normal and tangential contact forces to the contact particles. The proposed method is fully accelerated by GPU-based parallel computing. After verification, the performance of the proposed method is compared with the serial finite element code Abaqus/Explicit by testing two large-scale contact examples. The maximum speedup of the proposed method over Abaqus/Explicit is approximately 80 for the overall computation and 340 for contact calculations. Therefore, the proposed method is shown to be effective and efficient.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89346881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shuangxi Liu, B. Yan, Wei Huang, Xu Zhang, Jie Yan
临近空间高超声速飞行器是指在临近空间能够以大于5马赫速度飞行的一类飞行器, 具有飞行速度快、 突防能力强、 作战半径大和响应迅速等特点. 凭借其优异的性能优势, 高超声速飞行器逐渐成为各个国家新的空天博弈焦点, 给现有防御体系带来巨大挑战. 为满足临近空间高超声速飞行器防御需求, 本文系统性地梳理高超声速飞行器的“五大优势”及拦截高超声速飞行器的“四大难点”. 其次, 针对现阶段高超声速飞行器拦截制导律, 对基于单弹制导律和多弹协同制导律进行综述, 并归纳其优缺点. 最后, 从“信息域”、 “空间域”、 “物理域”和“效费比”四个方面对协同拦截高超声速飞行器未来发展方向进行了展望, 为临近空间拦截制导技术研究提供参考. The unique performance advantages of hypersonic vehicles represent a critical challenge for existing defense systems. To facilitate defensive operations against hypersonic vehicles in near space, this paper systematically discusses both the advantages of these vehicles and the difficulties in intercepting them. Focusing on the state-of-the-art terminal guidance laws for intercepting hypersonic vehicles in near space, we examine research progress in the area of single- and multi-interceptor cooperative guidance laws and summarize their advantages and disadvantages. We also highlight future research directions for developing an effective terminal guidance law for multi-interceptor cooperative interception of hypersonic vehicles, based on four aspects: the information domain, space domain, physical domain, and effect-cost ratio. The findings provide a reference for further research into near-space interceptor terminal guidance technologies.
临近空间高超声速飞行器是指在临近空间能够以大于5马赫速度飞行的一类飞行器, 具有飞行速度快、 突防能力强、 作战半径大和响应迅速等特点. 凭借其优异的性能优势, 高超声速飞行器逐渐成为各个国家新的空天博弈焦点, 给现有防御体系带来巨大挑战. 为满足临近空间高超声速飞行器防御需求, 本文系统性地梳理高超声速飞行器的“五大优势”及拦截高超声速飞行器的“四大难点”. 其次, 针对现阶段高超声速飞行器拦截制导律, 对基于单弹制导律和多弹协同制导律进行综述, 并归纳其优缺点. 最后, 从“信息域”、 “空间域”、 “物理域”和“效费比”四个方面对协同拦截高超声速飞行器未来发展方向进行了展望, 为临近空间拦截制导技术研究提供参考. The unique performance advantages of hypersonic vehicles represent a critical challenge for existing defense systems. To facilitate defensive operations against hypersonic vehicles in near space, this paper systematically discusses both the advantages of these vehicles and the difficulties in intercepting them. Focusing on the state-of-the-art terminal guidance laws for intercepting hypersonic vehicles in near space, we examine research progress in the area of single- and multi-interceptor cooperative guidance laws and summarize their advantages and disadvantages. We also highlight future research directions for developing an effective terminal guidance law for multi-interceptor cooperative interception of hypersonic vehicles, based on four aspects: the information domain, space domain, physical domain, and effect-cost ratio. The findings provide a reference for further research into near-space interceptor terminal guidance technologies.
{"title":"Current status and prospects of terminal guidance laws for intercepting hypersonic vehicles in near space: a review","authors":"Shuangxi Liu, B. Yan, Wei Huang, Xu Zhang, Jie Yan","doi":"10.1631/jzus.A2200423","DOIUrl":"https://doi.org/10.1631/jzus.A2200423","url":null,"abstract":"临近空间高超声速飞行器是指在临近空间能够以大于5马赫速度飞行的一类飞行器, 具有飞行速度快、 突防能力强、 作战半径大和响应迅速等特点. 凭借其优异的性能优势, 高超声速飞行器逐渐成为各个国家新的空天博弈焦点, 给现有防御体系带来巨大挑战. 为满足临近空间高超声速飞行器防御需求, 本文系统性地梳理高超声速飞行器的“五大优势”及拦截高超声速飞行器的“四大难点”. 其次, 针对现阶段高超声速飞行器拦截制导律, 对基于单弹制导律和多弹协同制导律进行综述, 并归纳其优缺点. 最后, 从“信息域”、 “空间域”、 “物理域”和“效费比”四个方面对协同拦截高超声速飞行器未来发展方向进行了展望, 为临近空间拦截制导技术研究提供参考. The unique performance advantages of hypersonic vehicles represent a critical challenge for existing defense systems. To facilitate defensive operations against hypersonic vehicles in near space, this paper systematically discusses both the advantages of these vehicles and the difficulties in intercepting them. Focusing on the state-of-the-art terminal guidance laws for intercepting hypersonic vehicles in near space, we examine research progress in the area of single- and multi-interceptor cooperative guidance laws and summarize their advantages and disadvantages. We also highlight future research directions for developing an effective terminal guidance law for multi-interceptor cooperative interception of hypersonic vehicles, based on four aspects: the information domain, space domain, physical domain, and effect-cost ratio. The findings provide a reference for further research into near-space interceptor terminal guidance technologies.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90416749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
目 的 在使用引射器的基础上, 低温风洞排气系统利用风机和加热器可进一步降低排气羽流的沉降危害, 但也带来了高能耗. 本文旨在探讨排气出口倾斜角度对低温风洞低温氮气排气过程的影响, 并验证采用倾斜排气出口结构对降低低温风洞排气系统能耗的可行性. 创新点 1. 提出低温风洞倾斜出口排气方式; 2. 建立低温风洞排气塔缩比模型, 并开展倾斜出口排气过程的实验分析. 方 法 1. 根据相似性准则, 建立低温风洞排气塔缩比模型, 并通过实验对比倾斜出口排气过程和传统垂直出口排气过程, 验证倾斜出口排气方式是否可降低羽流沉降危害; 2. 通过实验与模拟对比, 验证低温羽流扩散数值模型的准确性; 3. 通过仿真模拟, 进一步量化研究倾斜出口排气方式的节能潜力. 结 论 1. 相比传统垂直排气方式, 30°或45°倾斜出口的排气方式可有效降低低温羽流的沉降危害; 2. 以0.3 m低温风洞极端排气工况为例, 采用30°或45°倾斜出口, 在无风条件下可节省15.9%的加热能耗; 3. 采用倾斜出口排气方式可以提高排气系统的安全下限. A new structural design for the vent stack with an inclined exit was proposed to reduce the settlement hazard of the cryogenic plume from a cryogenic wind tunnel; it extends the plume trajectory to increase the effective contact space and time for mixing between the plume gas and atmospheric air before the plume settles to the ground, contributing to more efficient energy consumption for heating. Reduced-scale experiments and numerical simulations of plume dispersion based on vertical and 30°- and 45°-inclined exits were conducted to study harm reduction and energy-saving potential. Analyses of the minimum temperature and minimum oxygen concentration of the plume near the ground indicate that the new exhaust design with an inclined exit clearly reduces the settlement hazard. Under windless conditions and without using a fan-ejector system, up to 15.9% of the heating energy used by the burner can be saved by adopting the new design.
目 的 在使用引射器的基础上, 低温风洞排气系统利用风机和加热器可进一步降低排气羽流的沉降危害, 但也带来了高能耗. 本文旨在探讨排气出口倾斜角度对低温风洞低温氮气排气过程的影响, 并验证采用倾斜排气出口结构对降低低温风洞排气系统能耗的可行性. 创新点 1. 提出低温风洞倾斜出口排气方式; 2. 建立低温风洞排气塔缩比模型, 并开展倾斜出口排气过程的实验分析. 方 法 1. 根据相似性准则, 建立低温风洞排气塔缩比模型, 并通过实验对比倾斜出口排气过程和传统垂直出口排气过程, 验证倾斜出口排气方式是否可降低羽流沉降危害; 2. 通过实验与模拟对比, 验证低温羽流扩散数值模型的准确性; 3. 通过仿真模拟, 进一步量化研究倾斜出口排气方式的节能潜力. 结 论 1. 相比传统垂直排气方式, 30°或45°倾斜出口的排气方式可有效降低低温羽流的沉降危害; 2. 以0.3 m低温风洞极端排气工况为例, 采用30°或45°倾斜出口, 在无风条件下可节省15.9%的加热能耗; 3. 采用倾斜出口排气方式可以提高排气系统的安全下限. A new structural design for the vent stack with an inclined exit was proposed to reduce the settlement hazard of the cryogenic plume from a cryogenic wind tunnel; it extends the plume trajectory to increase the effective contact space and time for mixing between the plume gas and atmospheric air before the plume settles to the ground, contributing to more efficient energy consumption for heating. Reduced-scale experiments and numerical simulations of plume dispersion based on vertical and 30°- and 45°-inclined exits were conducted to study harm reduction and energy-saving potential. Analyses of the minimum temperature and minimum oxygen concentration of the plume near the ground indicate that the new exhaust design with an inclined exit clearly reduces the settlement hazard. Under windless conditions and without using a fan-ejector system, up to 15.9% of the heating energy used by the burner can be saved by adopting the new design.
{"title":"Exhaust process of cryogenic nitrogen gas from a cryogenic wind tunnel with an inclined exit","authors":"Jing-feng Li, Kai Wang, Chenjie Gu, Limin Qiu","doi":"10.1631/jzus.A2200289","DOIUrl":"https://doi.org/10.1631/jzus.A2200289","url":null,"abstract":"目 的 在使用引射器的基础上, 低温风洞排气系统利用风机和加热器可进一步降低排气羽流的沉降危害, 但也带来了高能耗. 本文旨在探讨排气出口倾斜角度对低温风洞低温氮气排气过程的影响, 并验证采用倾斜排气出口结构对降低低温风洞排气系统能耗的可行性. 创新点 1. 提出低温风洞倾斜出口排气方式; 2. 建立低温风洞排气塔缩比模型, 并开展倾斜出口排气过程的实验分析. 方 法 1. 根据相似性准则, 建立低温风洞排气塔缩比模型, 并通过实验对比倾斜出口排气过程和传统垂直出口排气过程, 验证倾斜出口排气方式是否可降低羽流沉降危害; 2. 通过实验与模拟对比, 验证低温羽流扩散数值模型的准确性; 3. 通过仿真模拟, 进一步量化研究倾斜出口排气方式的节能潜力. 结 论 1. 相比传统垂直排气方式, 30°或45°倾斜出口的排气方式可有效降低低温羽流的沉降危害; 2. 以0.3 m低温风洞极端排气工况为例, 采用30°或45°倾斜出口, 在无风条件下可节省15.9%的加热能耗; 3. 采用倾斜出口排气方式可以提高排气系统的安全下限. A new structural design for the vent stack with an inclined exit was proposed to reduce the settlement hazard of the cryogenic plume from a cryogenic wind tunnel; it extends the plume trajectory to increase the effective contact space and time for mixing between the plume gas and atmospheric air before the plume settles to the ground, contributing to more efficient energy consumption for heating. Reduced-scale experiments and numerical simulations of plume dispersion based on vertical and 30°- and 45°-inclined exits were conducted to study harm reduction and energy-saving potential. Analyses of the minimum temperature and minimum oxygen concentration of the plume near the ground indicate that the new exhaust design with an inclined exit clearly reduces the settlement hazard. Under windless conditions and without using a fan-ejector system, up to 15.9% of the heating energy used by the burner can be saved by adopting the new design.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74045708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shuiguang Tong, Zilong Fu, Zhe-ming Tong, Junjie Li, F. Cong
Condition monitoring and fault diagnosis of gearboxes play an important role in the maintenance of mechanical systems. The vibration signal of gearboxes is characterized by complex spectral structure and strong time variability, which brings challenges to fault feature extraction. To address this issue, a new demodulation technique, based on the Fourier decomposition method and resonance demodulation, is proposed to extract fault-related information. First, the Fourier decomposition method decomposes the vibration signal into Fourier intrinsic band functions (FIBFs) adaptively in the frequency domain. Then, the original signal is segmented into short-time vectors to construct double-row matrices and the maximum singular value ratio method is employed to estimate the resonance frequency. Then, the resonance frequency is used as a criterion to guide the selection of the most relevant FIBF for demodulation analysis. Finally, for the optimal FIBF, envelope demodulation is conducted to identify the fault characteristic frequency. The main contributions are that the proposed method describes how to obtain the resonance frequency effectively and how to select the optimal FIBF after decomposition in order to extract the fault characteristic frequency. Both numerical and experimental studies are conducted to investigate the performance of the proposed method. It is demonstrated that the proposed method can effectively demodulate the fault information from the original signal. 目 的 齿轮箱的振动信号频谱结构比较复杂, 难以提取其故障特征频率. 傅里叶分解方法可以将振动信号分解为多个单分量信号, 利用共振频率筛选出最优分量并进行包络解调, 识别特征频率以实现故障诊断. 创新点 1. 为了求解共振频率, 提出一种基于短时向量的最大奇异值比方法; 2. 将傅里叶分解方法引入到齿轮箱故障诊断中, 并利用共振频率选择最优分量进行包络解调以提取故障特征频率. 方 法 1. 分析奇异值比与冲击信号的关系, 提出求解共振频率的最大奇异值比方法; 2. 对比最大奇异值比方法与谱峭度方法在求解共振频率方面的表现, 从而验证最大奇异值比方法的有效性; 3. 对比分析所提方法与传统的总体经验模态分解 (EEMD) 和变分模态分解 (VMD) 方法在信号分解与故障特征提取方面的效果, 并通过仿真和实验进行验证. 结 论 1. 最大奇异值比方法能够准确计算出共振频率, 比谱峭度方法求解的频率值更加精确; 2. 基于傅里叶分解方法和最大奇异值比的共振解调方法能够有效提取故障特征频率, 其在故障诊断方面的表现优于EEMD和VMD方法.
{"title":"Fault diagnosis for gearboxes based on Fourier decomposition method and resonance demodulation","authors":"Shuiguang Tong, Zilong Fu, Zhe-ming Tong, Junjie Li, F. Cong","doi":"10.1631/jzus.A2200555","DOIUrl":"https://doi.org/10.1631/jzus.A2200555","url":null,"abstract":"Condition monitoring and fault diagnosis of gearboxes play an important role in the maintenance of mechanical systems. The vibration signal of gearboxes is characterized by complex spectral structure and strong time variability, which brings challenges to fault feature extraction. To address this issue, a new demodulation technique, based on the Fourier decomposition method and resonance demodulation, is proposed to extract fault-related information. First, the Fourier decomposition method decomposes the vibration signal into Fourier intrinsic band functions (FIBFs) adaptively in the frequency domain. Then, the original signal is segmented into short-time vectors to construct double-row matrices and the maximum singular value ratio method is employed to estimate the resonance frequency. Then, the resonance frequency is used as a criterion to guide the selection of the most relevant FIBF for demodulation analysis. Finally, for the optimal FIBF, envelope demodulation is conducted to identify the fault characteristic frequency. The main contributions are that the proposed method describes how to obtain the resonance frequency effectively and how to select the optimal FIBF after decomposition in order to extract the fault characteristic frequency. Both numerical and experimental studies are conducted to investigate the performance of the proposed method. It is demonstrated that the proposed method can effectively demodulate the fault information from the original signal. 目 的 齿轮箱的振动信号频谱结构比较复杂, 难以提取其故障特征频率. 傅里叶分解方法可以将振动信号分解为多个单分量信号, 利用共振频率筛选出最优分量并进行包络解调, 识别特征频率以实现故障诊断. 创新点 1. 为了求解共振频率, 提出一种基于短时向量的最大奇异值比方法; 2. 将傅里叶分解方法引入到齿轮箱故障诊断中, 并利用共振频率选择最优分量进行包络解调以提取故障特征频率. 方 法 1. 分析奇异值比与冲击信号的关系, 提出求解共振频率的最大奇异值比方法; 2. 对比最大奇异值比方法与谱峭度方法在求解共振频率方面的表现, 从而验证最大奇异值比方法的有效性; 3. 对比分析所提方法与传统的总体经验模态分解 (EEMD) 和变分模态分解 (VMD) 方法在信号分解与故障特征提取方面的效果, 并通过仿真和实验进行验证. 结 论 1. 最大奇异值比方法能够准确计算出共振频率, 比谱峭度方法求解的频率值更加精确; 2. 基于傅里叶分解方法和最大奇异值比的共振解调方法能够有效提取故障特征频率, 其在故障诊断方面的表现优于EEMD和VMD方法.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78872042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Improving the freeze-thaw resistance of geopolymers is of great significance to ensure their durability in cold regions. This study presents an experimental investigation of optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures. Firstly, five kinds of geopolymer composites with 10.0%, 20.0%, 30.0%, 40.0%, and 50.0% slag contents and 1.0% fiber content were prepared. Freeze-thaw cycle tests at −1.0 ℃, −20.0 ℃, and −40.0 ℃ were carried out for these geopolymer composites and their physical and mechanical properties after the freeze-thaw cycle were tested. The results show that the porosity of the geopolymer composites decreases as the slag content increases. Their mass loss ratio and strength loss ratio increase gradually as the freezing temperature decreases. The mass loss ratio and strength loss ratio of geopolymer composites after freeze-thaw cycles all decrease as the slag content increases. Considering the physical and mechanical properties of geopolymers after freeze-thaw cycles, the optimal slag contents are 40.0% and 50.0%. 目的 提高地聚物的抗冻融循环性能对确保地聚物在寒区中的耐久性具有重要意义。本文旨在研究冻结温度对矿渣改性的偏高岭土基地聚物物理和力学性能的影响,以期为地聚物在寒区中的实际应用和耐久性评估提供参考。 创新点 提出了冻融循环条件下地聚物复合材料的最佳矿渣含量;2. 发现矿渣的掺入可以抑制地聚物在寒冷环境中的开裂,提高地聚物复合材料的抗冻融性。 方法 制备不同矿渣的纤维增强聚合物并对其开展三种冻结温度的冻融循环试验;2. 分析不同矿渣的纤维增强聚合物的孔隙结构特性;3. 分析冻融循环后不同矿渣的纤维增强聚合物的物理力学性能;4. 提出冻融循环作用下地聚物复合材料的最佳矿渣含量。 结论 随着矿渣含量的增加,地聚物复合材料的孔隙率降低,且凝胶孔和过渡孔均逐渐减小;2. 冻融循环后,地聚物复合材料中的裂缝宽度和数量都随着矿渣含量的增加而减少,表明矿渣的掺入可以抑制地聚物在寒冷环境中的开裂;3. 矿渣的掺入可以显著降低地聚物复合材料在冻融循环后的质量损失率和强度损失率,进而提高地聚物复合材料的抗冻融性;4. 40.0%和50.0%矿渣含量的地聚物复合材料在冻融循环后仍能保持较高的力学性能。
{"title":"Optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures","authors":"L. Fan, Weiliang Zhong, Guang Wang, Y. Xi","doi":"10.1631/jzus.A2200437","DOIUrl":"https://doi.org/10.1631/jzus.A2200437","url":null,"abstract":"Improving the freeze-thaw resistance of geopolymers is of great significance to ensure their durability in cold regions. This study presents an experimental investigation of optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures. Firstly, five kinds of geopolymer composites with 10.0%, 20.0%, 30.0%, 40.0%, and 50.0% slag contents and 1.0% fiber content were prepared. Freeze-thaw cycle tests at −1.0 ℃, −20.0 ℃, and −40.0 ℃ were carried out for these geopolymer composites and their physical and mechanical properties after the freeze-thaw cycle were tested. The results show that the porosity of the geopolymer composites decreases as the slag content increases. Their mass loss ratio and strength loss ratio increase gradually as the freezing temperature decreases. The mass loss ratio and strength loss ratio of geopolymer composites after freeze-thaw cycles all decrease as the slag content increases. Considering the physical and mechanical properties of geopolymers after freeze-thaw cycles, the optimal slag contents are 40.0% and 50.0%. 目的 提高地聚物的抗冻融循环性能对确保地聚物在寒区中的耐久性具有重要意义。本文旨在研究冻结温度对矿渣改性的偏高岭土基地聚物物理和力学性能的影响,以期为地聚物在寒区中的实际应用和耐久性评估提供参考。 创新点 提出了冻融循环条件下地聚物复合材料的最佳矿渣含量;2. 发现矿渣的掺入可以抑制地聚物在寒冷环境中的开裂,提高地聚物复合材料的抗冻融性。 方法 制备不同矿渣的纤维增强聚合物并对其开展三种冻结温度的冻融循环试验;2. 分析不同矿渣的纤维增强聚合物的孔隙结构特性;3. 分析冻融循环后不同矿渣的纤维增强聚合物的物理力学性能;4. 提出冻融循环作用下地聚物复合材料的最佳矿渣含量。 结论 随着矿渣含量的增加,地聚物复合材料的孔隙率降低,且凝胶孔和过渡孔均逐渐减小;2. 冻融循环后,地聚物复合材料中的裂缝宽度和数量都随着矿渣含量的增加而减少,表明矿渣的掺入可以抑制地聚物在寒冷环境中的开裂;3. 矿渣的掺入可以显著降低地聚物复合材料在冻融循环后的质量损失率和强度损失率,进而提高地聚物复合材料的抗冻融性;4. 40.0%和50.0%矿渣含量的地聚物复合材料在冻融循环后仍能保持较高的力学性能。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87343844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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